<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>字体</title>
    <style>
        h3 {
            font-weight: 400;
        }

        em{
            font-style: italic;
        }

        div {
            font-weight: 700;
            font-style: italic;
        }
    </style>
</head>

<body>
    <h3>h3 标题</h3>
    <div>div 标签</div>

    <em>em标签</em>
    <div>div标签</div>
</body>

</html>